Their strategy is generally to sync just one folder (and all its subfolders) to the cloud, and in some cases, to offer online collaborative document editing. Those services do store files in the cloud, but they aren't designed to automatically protect all important documents and media files, let alone system files. Online backup services shouldn't be confused with cloud storage and file syncing services like Dropbox, Google Drive, and OneDrive. Once your files are uploaded, you can access and restore your data from anywhere. Online backup services scan your hard drive for files worth protecting, encrypt them for security, and send them up to the company's online servers. Even if you're among the very few who diligently perform local backups at regular intervals, you could still lose data if you don't store backups off-site. Natural disasters such as fires, floods, and earthquakes can also spell the end of your digital media and documents.
An online backup service is one of the best ways to protect yourself against data loss if, for example, your hard drive crashes, you accidentally delete important files, or you fall victim to a ransomware attack.